The present invention relates to a cutting tool assembly for rotary cutting and/or machining, comprising a tool body and a replaceable cutting head. More particularly, the present invention relates to a cutting tool having a replaceable cutting head retained on a tool body by a retaining system, wherein the cutting head comprises a unique mating surface configuration enabling an increased retention force on the cutting head while providing optimized torque transferability.
It is previously known to provide rotary cutting tools, such as drills, with replaceable cutting heads or drill tips. These tips have been retained on a tool body by many methods including radial set screws secured through lands provided on the tool body, press fit connections using dove-tail profiles, axial screws and drawbars, etc. While each method has different advantages and disadvantages, none of these tools can be easily and quickly replaced while maintaining optimized torque transferability, high feed rates, and a secure mounting to the tool body. Some prior tools of this type have worked well but have not been generally usable in aggressive machining operations, which produce high stress on the connection of the cutting head to the tool body.
Several examples of prior art configurations use a dovetail profile to connect the cutting head to the tool body. The cutting head is inserted into a recess generally having at least one radial base surface. The cutting head is then rotated such that a dovetail profile on the cutting head engages a dovetail recess of the tool body. This engagement is typically an interference fit type arrangement such that the cutting head is prevented from rotating in a disengaging direction. In order for the interference fit to provide sufficient retaining force, high stresses result at the tool body interface with the cutting head and in some cases, a special tool is needed to connect and disconnect the cutting head. Another problem with such a connection is that the feed force during operation of the tool pushes the cutting head downward into the tool body, which can lessen the retaining force of the dovetail connection and permit the cutting head to loosen.
Other examples of connecting the cutting head use an axial engagement bar to secure the cutting head to the tool body. Although attempting to clamp the head to the body, the high stress at the interface again may result in loosening of the connection and/or make the tool susceptible to eccentric and other loads.
It is also found in various tools with replaceable cutting heads, that it may be impossible to change the cutting head while the tool is mounted in an associated tool holder or machine. Thus, it is required that the entire tool be removed from the tool holder or machine, the cutting head then being replaced, and the tool being reintroduced into the machine for continued operation. Such a process adds labor and time, and detracts from the advantages of having the replaceable insert, and from the machining speeds achievable.
Accordingly, there remains a need in the art for a new drill assembly utilizing a replaceable cutting head which combines the advantages of a replaceable cutting head with the ability to be used in aggressive machining operations in which high stress conditions will exist. There also remains a need to provide drill assembly utilizing a replaceable cutting head which allows the cutting head to be replaced while the tool is mounted in the tool holder or machine to simplify and speed up this process.
It is therefore an object of the present invention to provide a new cutting tool assembly comprising a replaceable cutting head and a tool body having a common longitudinal axis and mating peripheral surfaces. The cutting head has a cutting portion forming a leading end, a pilot portion forming a trailing end, and a cutting head mounting portion adjacent the trailing end of the cutting head. The tool body has a cutting head receiving portion formed at a leading end of the tool body and a pilot recess disposed in the leading end of the tool body to matingly receive the pilot portion of the cutting head. The cutting head mounting portion and the cutting head receiving portion of the tool body each have at least two coupling portions. The cutting head coupling portions and the tool body coupling portions are bound by their peripheral surfaces and generally mate in shape and dimensions. Each coupling portion has a pair of base surfaces, including upper and lower surfaces. The base surfaces extend transversely to the longitudinal axis and provide support of the cutting head in the tool body. A torque transmission wall extends between the upper and lower base surfaces from the pilot portion surface in a generally transverse direction relative to the longitudinal axis and oriented transversely to the base surfaces. A fastener may be disposed in the tool body along its longitudinal axis where it matingly engages the pilot portion of the cutting head and exerts an axial force on the cutting head for pressing the cutting head mounting portion against the cutting head receiving portion of the tool body.